Pneumatic Tire

ABSTRACT

A tread pattern of a pneumatic tire includes one center continuous land portion and two intermediate continuous land portions that are divided by four circumferential main grooves and that are not provided with lug grooves. Edges on both sides of one center main groove include groove chamfered portions having a chamfered width changing in the circumferential direction in a zigzag shape. In the regions of the intermediate continuous land portions, first sipes extending inward in the lateral direction from shoulder main grooves of the main grooves, which are positioned on outer sides in the lateral direction, are provided. The first sipes each include a sipe main body portion having a constant distance between sipe wall surfaces on a sipe bottom side and a sipe chamfered portion inclined so that the sipe wall surfaces are open toward the tread surface.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/644,489, filed on Mar. 4, 2020, which is the National Stage ofInternational Patent Application No. PCT/JP2018/032092, filed on Aug.30, 2018, which claims the benefit of priority from Japan PatentApplication No. 2017-170858, filed on Sep. 6, 2017.

TECHNICAL FIELD

The present technology relates to a pneumatic tire.

BACKGROUND ART

For a pneumatic tire, on a tread portion, a tread pattern is formed inwhich a plurality of main grooves extending in a tire circumferentialdirection are provided and a plurality of rows of land portions aredefined by the plurality of main grooves. In such a pneumatic tire, gooddrainage performance is achieved by providing a plurality of lug groovesextending in a tire lateral direction in each of the land portions ofthe tread portion.

However, when the number of the lug grooves in the tread portion isincreased, the rigidity of the tread portion (tread rigidity) isdegraded, which degrades steering stability performance on dry roadsurfaces. In contrast, when the number of lug grooves in the treadportion is reduced, drainage performance is degraded, which degradessteering stability on wet road surfaces. Thus, steering stability on dryroad surfaces and steering stability on wet road surfaces areinconsistent with each other. Further, pattern noise is increased byproviding the lug grooves.

For example, a pneumatic tire capable of achieving steering stability ondry road surfaces and steering stability on wet road surfaces in acompatible manner and further improving uneven wear resistance has beenknown (see Japan Unexamined Patent Publication No. 2017-30556).

The pneumatic tire includes, in a tread portion, a center main grooveextending in tire circumferential direction in a zigzag shape along thetire circumferential direction and a shoulder main groove extending inthe tire circumferential direction on an outer side of the center maingroove. Further, the pneumatic tire includes, in land portions betweenthe center main groove and the shoulder main groove, a plurality of luggrooves, which extend inward in the tire lateral direction from theshoulder main groove and are terminated without communicating with thecenter main groove. At a terminating end of each of the lug grooves, abent portion that is bent toward one side in the tire circumferentialdirection is formed. In the land portions, a plurality of narrow groovesthat extend intermittently along the tire circumferential directionwithout communicating with the bent portions are formed. The narrowgrooves are disposed substantially parallel with the center groovehaving a zigzag shape.

The pneumatic tire described above is capable of achieving steeringstability performance on dry road surfaces and steering stabilityperformance on wet road surfaces in a compatible manner and furtherimproving uneven wear resistance performance. However, pattern noisecaused due to the lug grooves provided in the land portions is notreduced and remains loud. When the lug grooves are not provided in theland portions, steering stability performance on wet road surfaces isliable to be degraded.

SUMMARY

The present technology provides a pneumatic tire capable of improvingsteering stability performance on dry road surfaces and steeringstability performance on wet road surfaces compared to the related artand suppressing pattern noise.

An aspect of the present technology is a pneumatic tire. The pneumatictire, includes:

a tread portion extending in a tire circumferential direction, having anannular shape, and having a tread pattern, wherein

the tread pattern including:

two inner main grooves being positioned on both sides in a tire lateraldirection with respect to a tire equator line of the pneumatic tire andbeing formed in an entire circumference in the tire circumferentialdirection;

two outer main grooves being provided and sandwiching the two inner maingrooves on an inner side in the tire lateral direction;

an inner continuous land portion being sandwiched between the two innermain grooves and being continuously formed in the entire circumferencein the tire circumferential direction;

two intermediate continuous land portions being sandwiched between oneof the two inner main grooves and one of the two outer main grooves andbetween the other one of the two inner main grooves and the other one ofthe two outer main grooves, respectively, the two intermediatecontinuous land portions being continuously formed in the entirecircumference in the tire circumferential direction, the twointermediate continuous land portions being outward in the tire lateraldirection of the inner continuous land portion; and

first sipes being provided in regions of the two intermediate continuousland portions and extending inward in the tire lateral direction fromthe two outer main grooves.

Regions of the inner continuous land portion and the two intermediatecontinuous land portions being not provided with lug grooves extendingfrom the two inner main grooves or the two outer main grooves.

Edges on both sides of one of the two inner main grooves each includinga groove chamfered portion having a chamfered width changing in the tirecircumferential direction and forming a zigzag shape as seen from atread surface of the tread portion. The first sipes each including: asipe main body portion having a constant distance between sipe wallsurfaces on a sipe bottom side in a depth direction of the first sipes;and a sipe chamfered portion inclined so that the sipe wall surfaces areopen to the tread surface on a side of the tread surface of the firstsipes.

The first sipes are preferably provided to be inclined in the tirelateral direction from the two outer main grooves to the innercontinuous land portion and to be closed in the regions of the twointermediate continuous land portions. As seen from the tread surface, asurface contour shape of each of first sipes a of the first sipes, whichextends from an outer main groove A being one of the two outer maingrooves, preferably has: an extending portion extending constantly in anextension direction or with smooth change from the outer main groove A;and a bent portion provided on a side of a closed end portion of each ofthe first sipes a, the bent portion bending each of the first sipes afrom the extending portion and extending to a direction opposite adirection to which the extending portion extends in the tirecircumferential direction. In the bent portion, the sipe main bodyportion preferably extends from the extending portion constantly in theextension direction or with smooth change without being bent and isclosed, and the sipe chamfered portion preferably forms a bent shape ofthe bent portion.

Further, a sipe wall surface being one of two facing sipe wall surfacesof the sipe chamfered portion preferably includes a first chamferedsurface and a second chamfered surface at different positions in a sipedepth direction, an inclination angle of each of the first chamferedsurface and the second chamfered surface with respect to the depthdirection of the first sipes being different each other, and the sipechamfered portion preferably forms a bent shape of the bent portion.

The inclination angle of the first chamfered surface is preferablyidentical to that of a counter chamfered surface opposing the firstchamfered surface.

Further, the inclination angle of the second chamfered surface ispreferably larger than the inclination angle of the first chamferedsurface. In this case, the second chamfered surface is preferablypositioned on the side of the tread surface with respect to the firstchamfered surface.

A chamfered width of the two facing chamfered surfaces is preferablyreduced as approaching to a closed end of the sipe main body portion.

Narrow grooves each being prevented from communicating with the bentportion are preferably formed intermittently in the tire circumferentialdirection in a region of an intermediate continuous land portion α ofthe two intermediate continuous land portions in which the first sipes aare provided, and an extension direction of the narrow grooves ispreferably parallel with an extension direction of an edge of thesurface contour shape on a side of the two inner main grooves.

The pneumatic tire preferably has a mounting direction that is specifiedwith respect to a vehicle, and the outer main groove A preferably isinstructed, +−by the mounting direction to be positioned on an outervehicle side with respect to an outer main groove B of the two outermain grooves, the outer main groove B being different from the outermain groove A.

Second sipes are preferably provided in a region of an intermediatecontinuous land portion β of the two intermediate continuous landportions, which is sandwiched between an outer main groove of the twoouter main grooves different from the outer main groove A and one of thetwo inner main grooves, the second sipes extending from one of the twoinner main grooves and being closed without communicating with the outermain groove. Third sipes are preferably provided in the region of theinner continuous land portion, the third sipes extending from an innermain groove of the two inner main grooves, which is in contact with theintermediate continuous land portion β, to the other inner main grooveand being closed without communicating with the other inner main groove.Inclination directions of the second sipes and the third sipes withrespect to the tire lateral direction and positions thereof in the tirecircumference are preferably set, and the second sipes are positioned onextension lines of the third sipes.

As seen from the tread surface, first sipes b of the first sipes, whichare provided in a region of the intermediate continuous land portion β,and the second sipes are preferably inclined to different directions inthe tire circumferential direction as extending inward in the tirelateral direction.

As seen from the tread surface, the first sipes provided in the regionsof the two intermediate continuous land portions are preferably inclinedto different sides in the tire circumferential direction as extendinginward in the tire lateral direction.

An outer land portion is preferably provided on an outer side of theouter main groove B of the two outer main grooves in the tire lateraldirection. A circumferential auxiliary groove and outer lug grooves arepreferably provided in a region of the outer land portion, thecircumferential auxiliary groove formed in the entire circumference inthe tire circumferential direction, the outer lug grooves extending inthe tire lateral direction from the outer side in the tire lateraldirection and being closed without communicating with the outer maingroove B. The outer lug grooves preferably intersect the circumferentialauxiliary groove.

According to the pneumatic tire described above, steering stabilityperformance on dry road surfaces and steering stability performance onwet road surfaces can be improved compared to the related art, andpattern noise can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a profile cross-sectional view of a pneumatic tire accordingto an embodiment.

FIG. 2 is a developed view illustrating an example of a tread pattern ofthe pneumatic tire according to an embodiment.

FIGS. 3A and 3B are enlarged plan views illustrating an example of afirst sipe illustrated in FIG. 2.

FIGS. 4A and 4B are cross-sectional views of an example of the firstsipe illustrated in FIG. 3A.

FIG. 5 is a perspective view of an example of the first sipe when thefirst sipe illustrated in FIG. 3A is cut along a sipe center line.

FIG. 6 is an enlarged plan view illustrating main parts of the treadpattern illustrated in FIG. 2.

DETAILED DESCRIPTION

Hereinafter, a pneumatic tire of the present embodiment will bedescribed in detail.

In the present specification, “tire lateral direction” refers to thedirection of the center axis of rotation of a pneumatic tire. “Tirecircumferential direction” refers to a rotation direction in which atread surface rotates, when the tire rotates about the center axis ofrotation of the tire. “Tire radial direction” refers to the directionradiating from the center axis of rotation of the tire. “Outward in thetire radial direction” refers to the direction away from the center axisof rotation of the tire. “Inward in the tire radial direction” refers tothe direction towards the center axis of rotation of the tire. “Outwardin the tire lateral direction” refers to the direction away from thetire equator line in the tire lateral direction. “Inward in the tirelateral direction” refers to the direction toward the tire equator linein the tire lateral direction.

FIG. 1 is a profile cross-sectional view of the pneumatic tire accordingto an embodiment. A pneumatic tire T illustrated in FIG. 1 includes atread portion 1 having an annular shape and extending in the tirecircumferential direction, a pair of sidewall portions 2, 2 disposed onboth sides of the tread portion 1, and a pair of bead portions 3, 3disposed inward in the tire radial direction of the correspondingsidewall portions 2.

A carcass layer 4 is mounted between the pair of bead portions 3, 3. Thecarcass layer 4 includes a plurality of reinforcing cords extending inthe tire radial direction and is folded back around bead cores 5respectively disposed in the bead portions 3 from a tire inner side to atire outer side. A bead filler 6, extending outward in the tire radialdirection, having a triangular cross-sectional shape, and formed from arubber composition, is disposed on the outer circumference of the beadcore 5. Meanwhile, a plurality of belt layers 7 are embedded outward inthe tire radial direction of the carcass layer 4 in the tread portion 1.The belt layers 7 each include a plurality of reinforcing cords that areinclined with respect to the tire circumferential direction, thereinforcing cords being disposed between layers in a criss-cross manner.In the belt layers 7, the inclination angle of the reinforcing cordswith respect to the tire circumferential direction falls within a rangeof from 10° to 40°, for example. Steel cords are preferably used as thereinforcing cords of the belt layers 7. To improve high-speeddurability, at least one belt cover layer 8 is disposed outward in thetire radial direction of the belt layer 7, the belt cover layer 8 havingreinforcing cords arranged at an angle of 5° or less, for example, withrespect to the tire circumferential direction. Nylon, aramid, or similarorganic fiber cords are preferably used as the reinforcing cords of thebelt cover layer 8.

Note that the tire internal structure described above represents atypical example for a pneumatic tire, and the pneumatic tire is notlimited thereto.

FIG. 2 is a developed view illustrating an example of a tread pattern 10of the pneumatic tire T according to an embodiment. The pneumatic tire Thaving the tread pattern 10 may be suitably used for a passengervehicle.

In FIG. 2, a reference symbol CL denotes the tire center line (tireequator line).

The tread pattern 10 mainly includes center main grooves (inner maingrooves) 11, 12, shoulder main grooves (outer main grooves) 13, 14, acenter continuous land portion (inner continuous land portion) 21,intermediate continuous land portions 22, 23, and first sipes 30, 31.

The center main grooves 11, 12 are positioned on both sides in the tirelateral direction across a center line CL and are formed in the entirecircumference of the tread portion 1 in the tire circumferentialdirection. Edges on both groove sides of the center main groove 12include groove chamfered portions 12A, 12B, the groove chamferedportions 12A, 12B having a chamfered width changing in the tirecircumferential direction so as to have a zigzag shape as seen from thetread surface of the tread portion 1. On the edges on both groove sidesof the center main groove 12, one of the groove chamfered portions 12A,12B has a chamfered width that is gradually increased to reach apredetermined width as extending in one direction in the tirecircumferential direction, and another of the groove chamfered portions12A, 12B further starts from a position substantially same as thereached position and has a chamfered width that is gradually increasedfrom a chamfered width O to reach a predetermined width. By repeatingthis, the groove chamfered portions 12A, 12B are formed in the entirecircumference of the center main groove 12 in the tire circumferentialdirection. On the edges on both groove sides of the center main groove12, the chamfered width starts at the same position and ends at the sameposition in the tire circumferential direction, and hence the centermain groove 12 has a zigzag shape as seen from the tread surface.However, the groove width of the center main groove 12 is kept a certainwidth, and the center main groove 12 is formed in the entirecircumference. In the zigzag shape, regarding the position at which oneof the groove chamfered portions 12A. 12B ends and another of the groovechamfered portions 12A, 12B starts, a dimension of a step on the edge inthe tire lateral direction (length along the tire lateral direction)falls within a range of from 15% to 35% of the groove width of thecenter main groove 12, for example.

The center main groove 11 is not provided with a chamfered portion thatis similar to those provided to the center main groove 12. The edges onboth groove sides of the center main groove 11 extend linearly along theentire circumference of the tire in the tire circumferential direction.

The shoulder main grooves 13, 14 are provided so as to sandwich thecenter main grooves 11, 12 inward in the tire lateral direction andextend linearly along the entire circumference of the tread portion 1 inthe tire circumferential direction without being bent or curved.

The groove width of the center main grooves 11, 12 and the shoulder maingrooves 13, 14 falls within a range of from 5.0 mm to 15.0 mm, and thegroove depth thereof falls within a range of from 6.5 mm to 9.0 mm, forexample.

The center continuous land portion 21 is formed between the center maingrooves 11, 12 and formed continuously in the entire circumference inthe tire circumferential direction. The center line CL passes on thecenter continuous land portion 21.

The intermediate continuous land portion 22 is formed between the centermain groove 11 and the shoulder main groove 13 and is formed outward inthe tire lateral direction of the center continuous land portion 21 andformed in the entire circumference of the tread portion 1 in the tirecircumferential direction. The intermediate continuous land portion 23is also formed between the center main groove 12 and the shoulder maingroove 14 and is formed outward in the tire lateral direction of thecenter continuous land portion 21 and formed in the entire circumferenceof the tread portion 1 in the tire circumferential direction.

In regions of the center continuous land portion 21 and the intermediatecontinuous land portion 22, lug grooves extending from the center maingrooves 11, 12 or the shoulder main grooves 13, 14 are not provided atall and only sipes are provided. The lug groove referred hereinindicates a lug groove having a groove width between groove wallsexceeds 2 mm, at a position of 50% of each of positions in a groovedepth direction.

The first sipes 30 are provided in a region of the intermediatecontinuous land portion 23, extend inward in the tire lateral directionfrom the shoulder main groove 14, and are closed in the region of theintermediate continuous land portion 23 without contact with the centermain groove 12. The first sipes 31 are provided in a region of theintermediate continuous land portion 22, extend inward in the tirelateral direction from the shoulder main groove 13, and are closed inthe region of the intermediate continuous land portion 22 withoutcontact with the center main groove 11.

Shoulder land portions 24, 25 are provided outward in the tire lateraldirection of the shoulder main grooves 13, 14. The shoulder landportions 24, 25 are provided with a plurality of shoulder lug grooves35, 36, respectively. The shoulder lug grooves 35, 36 extend inward inthe tire lateral direction from the tread pattern ends on both sides inthe tire lateral direction, are closed in the regions of the shoulderland portions 24, 25 without contact with the shoulder main grooves 13,14, and are disposed at a predetermined interval in the tirecircumferential direction. Shoulder sipes 37, 38 are provided betweenthe shoulder lug grooves 35, 36 adjacent to each other in the tirecircumferential direction. The shoulder sipes 37, 38 are provided inwardin the tire lateral direction from the regions of the shoulder landportions 24, 25 so as to be parallel with the shoulder lug grooves 35,36 and are in contact with the shoulder main grooves 13, 14.

In such tread pattern 10, the first sipes 30, 31 each include: a sipemain body portion 40 on a sipe bottom side in a depth direction of thefirst sipes 30, 31, a distance between sipe wall surfaces in the sipemain body portion 40 being constant (see FIG. 4A); and a sipe chamferedportion 42 on a side of the tread surface of the first sipes 30, 31, thesipe chamfered portion 42 having the sipe wall surfaces inclined so asto open to the tread surface. That is, the first sipes 30, 31 areso-called chamfered sipes.

A depth of the first sipes 30, 31 falls within a range of from 5.5 mm to8.5 mm, for example. The depth of the first sipes 30, 31 is shallowerthan the groove depth of the center main grooves 11, 12 and shouldermain grooves 13, 14, and the distance between the sipe wall surfaces ofthe sipe main body portion 40 falls within a range from 0.3 mm to 0.9mm, for example. Generally, the distance between the sipe wall surfacesof the sipe falls within a range from 0.3 mm to 0.9 mm in a case wherethe sipe wall surfaces are parallel with each other. This distance isnarrower than the groove width of the main grooves such as the centermain grooves 11, 12 and the shoulder main grooves 13, 14. The sipe andthe main groove can be distinguished from each other by a difference ina distance between parallel sipe wall surfaces and in a dimension of agroove width.

As described above, lug grooves are not formed in the regions of theintermediate continuous land portions 22, 23. Thus, the degradation oftread rigidity of the intermediate continuous land portions 22, 23 issuppressed, and steering stability performance on dry road surfaces isimproved. Further, lug grooves are not formed in the center continuousland portion 21, and the degradation of tread rigidity is suppressed.Thus, steering performance at the initial stage of steering on dry roadsurfaces can also be improved. Meanwhile, the first sipes 30, 31provided in the intermediate continuous land portions 22, 23 arechamfered sipes, and hence water flows easily on the sipe chamferedportion 42 as compared to sipes without a sipe chamfered portion in therelated art. Further, since a part of the sipe chamfered portion 42functions as an edge and since the center main groove 12 is providedwith the groove chamfered portions 12A, 12B and the center main groove12 forms a zigzag shape, which functions as an edge, steering stabilityperformance on wet road surfaces is improved. Further, since lug groovesare not formed in the regions of the intermediate continuous landportions 22, 23 and the center continuous land portion 21 and sinceblocks are not formed by cutting the continuous land portion, patternnoise caused due to lug grooves is not caused. Thus, pattern noise isalso reduced.

In order to improve steering stability performance on wet road surfaces,an inclination angle θ of the sipe wall surfaces of the first sipes 30,31 with respect to the sipe depth direction (see FIGS. 4A and 4B)preferably falls within a range of from 20 degrees to 80 degrees, forexample. In the first sipes 30, 31, the length of the sipe chamferedportion 42 in the sipe depth direction is preferably constant regardlessof a position of the first sipes 30, 31 in the extension direction andpreferably falls within a range of from 25% to 60% of the length in thesipe depth direction (length from the tread surface to the sipe bottom),for example. Therefore, in the first sipes 30, 31, a length in the sipedepth direction, as seen from the tread surface, of a joint position ofthe sipe chamfered portion 42 and the sipe main body portion 40 ispreferably constant regardless of a position of the first sipes 30, 31in the extension direction.

FIGS. 3A and 3B are enlarged plan views illustrating an example of thefirst sipes 30, 31 in a preferred embodiment. FIGS. 4A and 4B arecross-sectional views of an example of the first sipes 30, 31illustrated in FIG. 3A. FIG. 5 is a perspective view of an example whenthe first sipe 30 illustrated in FIG. 3A is cut along a sipe center line45. FIG. 6 is an enlarged plan view illustrating main parts of the treatpattern 10.

As illustrated in FIG. 2, the first sipes 30, 31 extend so as to beinclined in the tire lateral direction from the shoulder main grooves13, 14 on a side of the center continuous land portion 21 and areprovided so as to be closed in the regions of the intermediatecontinuous land portions 22, 23. Of the first sipes 30, 31, a surfacecontour shape, which is seen from the tread surface, of each of thefirst sipes 30 (first sipes a) extending from the shoulder main groove14 (shoulder main groove A) includes: an extending portion 44 extendingconstantly in an extension direction or with smooth change from theshoulder main groove 14 (see FIG. 2 and FIG. 3A); and a bent portion 46being provided at a closed end portion of the first sipe 30 andextending from the extending portion 44 in a bent manner to a directionopposite the direction to which the extending portion 44 extends in thetire circumferential direction.

A bent shape similar to the bent portion 46 is not provided at a closedend portion of the first sipe 31. The first sipe 31 extends from theshoulder main groove 13 constantly in an extension direction or withsmooth change and is closed in the region of the intermediate continuousland portion 22 without contact with the center main groove 11. In thiscase, in the sipe depth direction, the sipe main body portion 40 and thesipe chamfered portion 42 extend to the closed end portion with across-sectional shape the same as that of the extending portion 44. Theinclination angle of the chamfered surface of the sipe chamfered portion42 with respect to the sipe depth direction remains as a constant anglewithout being changed.

In this case, according to an embodiment, as illustrated in FIG. 4B andFIG. 5, preferably in the bent portion 46 of the first sipe 30, the sipemain body portion 40 extends constantly in an extension direction orwith smooth change from the extending portion 44 without being bent andis closed, whereas the sipe chamfered portion 42 forms a bent shape ofthe bent portion.

Specifically, the bent shape of the bent portion 46 is preferably formedby changing an inclination angle θ of a chamfered surface 42A of thesipe chamfered portion 42 with respect to the depth direction of thefirst sipe 30 (see FIG. 4B). That is, a sipe wall surface on one side ofthe two sipe wall surfaces has the chamfered surface (first chamferedsurface) 42A and a chamfered surface (second chamfered surface) 42C,which have different inclination angles with respect to the depthdirection of the first sipe, at different positions in the sipe depthdirection. As described above, the bent shape of the bent portion 46 isformed.

As illustrated in FIG. 4A, a sipe cross-sectional shape at the extendingportion 44 of the first sipe 30 has a left-right symmetric shape withrespect to a sipe center line 45. The sipe chamfered portion 42 of theextending portion 44 is formed of the chamfered surface 42A and achamfered surface 42B that face each other. The chamfered surface 42Aand the chamfered surface 42B have the same inclination angle θ and areinclined to different directions with respect to the sipe depthdirection. The chamfered surface 42A and the chamfered surface 42B areflat surfaces but may be curved surfaces that are curved so as to besmoothly convex or concave with respect to a space between the sipe wallsurfaces.

In contrast, as illustrated in FIG. 4B, a sipe cross-sectional shape atthe bent portion 46 is asymmetric with respect to the sipe center line45. The sipe chamfered portion 42 of the bent portion 46 is formed ofthe chamfered surface 42A and the chamfered surface 42B facing eachother, the chamfered surface 42C, and a wall surface 42D. The chamferedsurface 42A and the chamfered surface 42B have the same inclinationangle θ but are inclined to different directions with respect to thesipe depth direction. The chamfered surface 42C is provided on the sameside and is inclined to the same side as the chamfered surface 42A. Theinclination angle θ of the chamfered surface 42C is different from thatof the chamfered surface 42A. According to an embodiment, theinclination angle θ of the chamfered surface 42C is preferably largerthan the inclination angle θ of the chamfered surface 42A. According toan embodiment, the chamfered surface 42C is preferably positioned on aside of the tread surface with respect to the chamfered surface 42A. Byadopting such a configuration, the space between the facing chamferedsurfaces of the sipe chamfered portion 42 can be largely secured.Therefore, the chamfered surface 42A and the chamfered surface 42C isjoined via a ridge line 42E. The chamfered surface 42C is a flat surfaceinclined from the tread surface in a direction toward a distal end ofthe closed end portion of the sipe main body portion 40 of the firstsipe 30. As illustrated in FIG. 3A, a surface contour shape of the bentportion 46 has an arrow shape, and edges held in contact with the treadsurface, shaping the arrow shape, are ridge lines 42F, 42G. Thechamfered surface 42C is joined to the tread surface via the ridge line42F. Therefore, the chamfered surface 42C is inclined from the ridgeline 42F to the position of the distal end of the closed end portion,which is the uppermost position of the sipe main body portion 40 in thesipe depth direction (joint position between the chamfered surface 42Aand the sipe wall surface of the sipe main body portion 40). Meanwhile,the wall surface 42D is joined to the tread surface via the ridge line42G and extends to the chamfered surface 42C at an inclination anglefalling within a range of from 0 degrees to 60 degrees with respect tothe sipe depth direction. That is, the wall surface 42D is a steepinclined surface as seen from the tread surface similarly to the sipewall surface of the sipe main body portion 40. As illustrated in FIG. 2and FIG. 6, such ridge line 42G forms an edge of the arrow shape of thebent portion 46 bent from the extending portion 44 in the tirecircumferential direction. Therefore, the ridge line 42G can exert anedge effect. Note that the chamfered surface 42A, the chamfered surface42B, the chamfered surface 42C, and the wall surface 42D are flatsurfaces but may be curved surfaces that are curved so as to be smoothlyconvex or concave with respect to a space between the sipe wallsurfaces.

According to an embodiment, as illustrated in FIG. 4B, the chamferedsurfaces 42A, 42C being the sipe wall surfaces on one side of the firstsipe 30 preferably have different inclination angles θ with respect tothe depth direction of the first sipe 30 so as to form the bent shape ofthe bent portion 46. With this, the inclination angle θ of the chamferedsurface 42C can be larger than the inclination angle θ of the chamferedsurface 42B, and a large space can be secured in the bent portion 46.Thus, water on wet road surfaces is more likely to flow in this spaceand is drained to the shoulder main groove 14 through the sipe chamferedportion 42, which contributes to drainage performance. Thus, steeringstability performance on wet road surfaces can be improved.

According to an embodiment, the inclination angle θ of the chamferedsurface 42A is preferably the same as that of the facing chamferedsurface 42B. With this, a portion near the first sipe 30 in theintermediate continuous land portion 23 can be prevented from beingdeformed in an extremely asymmetric manner, and block chipping can besuppressed.

Further, according to an embodiment, the chamfered width of the twochamfered surfaces 42A and 42C is preferably reduced toward the closedend of the sipe main body portion 40. As illustrated in FIG. 4B, thepositions of the chamfered surfaces 42A, 42C in the depth direction fromthe tread surface are deeper as approaching to the distal end of theclosed end of the sipe main body portion 40, and the chamfered widththereof is reduced as approaching to the distal end of the closed end ofthe sipe main body portion 40. Thus, the degradation of the treadrigidity of the intermediate continuous land portion 23 can besuppressed, and the degradation of steering stability on dry roadsurfaces can be suppressed.

As illustrated in FIG. 6, in the region of the intermediate continuousland portion 23 (intermediate continuous land portion α) in which thefirst sipes 30 (first sipes a) are provided, narrow grooves 60 that donot communicate with the bent portions 46 are provided intermittently inthe tire circumferential direction. According to an embodiment, theextension direction of the narrow groove 60 is preferably parallel withthe extension direction of the ridge line 42G being an edge of thesurface contour shape of the bent portion 46 on the center main groove12 side. The edge of the ridge line 42G and the edge of the narrowgroove 60 are parallel with each other, and thus the orientation of theedge components can be aligned, which increases an edge effect. Thus,steering stability performance on wet road surfaces can be improved. Thegroove width of the narrow groove 60 falls within a range from 0.2 mm to1.0 mm, for example, and the groove depth thereof falls within a rangeof from 2.0 mm to 4.0 mm, for example. Thus, the narrow groove 60 can bedistinguished from a lug groove and a main groove by its groove depthand groove width.

According to an embodiment, the pneumatic tire T preferably has aspecified mounting direction with respect to a vehicle. Thisspecification of the mounting direction is indicated as information withcharacters, symbols, or the like on a sidewall surface of the pneumatictire T. In this case, the mounting direction is preferably specified sothat the shoulder main groove 14 (shoulder main groove A) and the centermain groove 12 in a zigzag shape are positioned on the vehicle outerside with respect to the shoulder main groove 13 (shoulder main grooveB) and the center main groove 11. A heavy load is applied to a corneringouter side of the pneumatic tire at the time of cornering, which largelyaffects steering stability performance. On such cornering outer side ofthe pneumatic tire, the edge components of the center main groove 12 ina zigzag shape, the first sipes 30, and the narrow grooves 60, which arepositioned on the vehicle outer side with respect to the center line CL,further improves steering stability performance on wet road surfaces.

Further, as illustrated in FIG. 2, in the region of the intermediatecontinuous land portion 22 (intermediate continuous land portion β),second sipes 32, which extend from the center main groove 11 and areclosed without contact with the shoulder main groove 13, are provided,and third sipes 33, which extend from the center main groove 11 held incontact with the intermediate continuous land portion 22 to the centermain groove 12 on the opposite side and are closed without contact withthe center main groove 12 on the opposite side, are further provided. Inthis case, according to an embodiment, as illustrated in FIG. 2,inclination angles of the second sipes 32 and the third sipes 33 withrespect to the tire lateral direction and positions thereof in the tirecircumference are preferably set so that the second sipes 32 arepositioned on the extension lines of the third sipes 33. With this, thesecond sipe 32 and the third sipe 33 act like one sipe, and an edgeeffect is exerted in a concentrated manner. Thus, braking and drivingperformance on wet road surfaces can be improved. Each of the secondsipes 32 and the third sipes 33 is a sipe configured without a sipechamfered portion, which has facing sipe wall surfaces parallel witheach other at any position in the sipe depth direction.

Further, as seen from the tread surface, the first sipes 31 (first sipesb) and the second sipes 32 formed in the region of the intermediatecontinuous land portion 22 (intermediate continuous land portion β) arepreferably inclined to different directions in the tire circumferentialdirection with respect to a direction toward the same side in the tirelateral direction (the left side or the right side on the drawing sheetof FIG. 2). That is, the first sipe 31 and the second sipe 32 form achevron shape. With this, even when the pneumatic tire T is at apositive slip angle or a negative slip angle, steering stabilityperformance and braking and driving performance on wet road surfaces canbe effectively exerted.

As seen from the tread surface, the first sipes 30, 31 are preferablyinclined to the same direction in the tire circumferential directionwith respect to a direction toward the same side in the tire lateraldirection (the left side or the right side on the drawing sheet of FIG.2). In other words, it can be said that, as seen from the tread surface,the first sipes 30, 31 are inclined to different sides in the tirecircumferential direction as extending inward in the tire lateraldirection. In the example illustrated in FIG. 2, the first sipes 30, 31extend right upward from the lower left or extend left downward from theupper right on the drawing sheet. The inclination angle of the firstsipes 30, 31 with respect to the tire circumferential directionpreferably falls within a range of from 25 degrees to 75 degrees. Whenthe inclination angle is less than 25 degrees, in the vicinities of theconnection portions in which the first sipes 30, 31 are in contact withthe shoulder main grooves 13, 14, the tread rigidity of the intermediatecontinuous land portion 23 is locally degraded, and steering stabilityperformance on dry road surfaces is more likely to be degraded, which ismore likely to be a main cause for uneven wear. When the inclinationangle is more than 75 degrees, the tread rigidity of the intermediatecontinuous land portion 23 in the tire circumferential direction isdegraded, and steering stability performance on dry road surfaces ismore likely to be degraded.

Further, as illustrated in FIG. 2, in the region of the shoulder landportion 24, a circumferential auxiliary groove 39 formed in the entirecircumference in the tire circumferential direction and the shoulder luggrooves 36 are provided. The shoulder lug grooves 36 extend in the tirelateral direction from an outer side in the tire lateral direction andare closed without communicating with the shoulder main groove 13(shoulder lug groove B). In this case, the shoulder lug grooves 36preferably intersect the circumferential auxiliary groove 39. Thecircumferential auxiliary groove 39 prevents the tread rigidity of theshoulder land portion 24 from being excessively increased and adjusts aground contact area of the shoulder land portion. Particularly, when theshoulder land portion 24 is mounted to a vehicle so as to be oriented toa vehicle inner side, a ground contact area of the tire can be increasedto reduce a ground contact pressure due to an effect of an camber(negative camber). Thus, wear of the shoulder land portion 24 can besuppressed.

The groove width of the circumferential auxiliary groove 39 falls withina range from 0.8 mm to 3.0 mm, for example, and the groove depth thereoffalls within a range from 1.0 mm to 4.5 mm, for example.

EXPERIMENT

In order to confirm the effects of the pneumatic tire T according to thepresent embodiment, pneumatic test tires having various tread patternswere produced and subjected to performance evaluation. Specifically,each produced pneumatic test tire had a tire size of 225/50R17 98W. Eachproduced pneumatic test tire was mounted to a rim (rim size of 17×7.5 J)and was mounted to a test vehicle (front wheel drive vehicle with enginedisplacement of 2400 cc) under a condition of an air pressure of 230kPa. The test vehicle traveled on a test course road surface, andevaluation on steering stability performance on dry road surfaces andsteering stability performance on wet road surfaces and evaluation on amagnitude of pattern noise were performed.

With regard to evaluation on steering stability performance on dry roadsurfaces, while performing steering on dry road surfaces, a driverperformed sensory evaluation on response corresponding to steering, andConventional Example was indexed as an index value of 100. Larger indexvalues indicate better performance.

With regard to evaluation on steering stability performance on wet roadsurfaces, a travel time required for traveling on a predetermined rangeof wet road surfaces on which rainy weather conditions were reproducedwas measured, and a multiplicative inverse thereof was indexed. Amultiplicative inverse of a measured travel time in Conventional Examplewas set as an index value of 100. Thus, larger index values indicatebetter performance.

With regard to evaluation on pattern noise, sensory evaluation wasperformed on a magnitude of pattern noise sensed by a driver at the timeof causing a vehicle to travel under a predetermined speed condition.Evaluation was performed by indexing Conventional Example as an indexvalue of 100. Larger index values indicate lower pattern noise.

The produced pneumatic test tires T each had a tire structureillustrated in FIG. 1.

A tread pattern of the pneumatic tire in Conventional Example had atread pattern illustrated in FIG. 2 except for providing lug grooves inplace of the first sipes 30, 31 in the tread pattern illustrated in FIG.2. The groove width of the lug grooves was set to 4.6 mm.

In Comparative Example, the tread pattern illustrated in FIG. 2 was setas a basic pattern in which the first sipes 30, 31 were provided, butthe sipes were each formed of the sipe main body portion 40 that was notprovided with the sipe chamfered portion 42 and that had a constantdistance between the facing sipe wall surfaces in the sipe depthdirection. The distance between the sipe wall surfaces was set to thesame as that in the sipe main body portion 40 in Examples describedbelow. The sipe depths of the first sipes 30, 31 was set to 5.7 mm, thedistance between the sipe wall surfaces of the sipe main body portion 40was set to 0.6 mm, the inclination angle θ of the chamfered surfaces42A, 42B was set to 25 degrees, the inclination angle θ of the chamferedsurface 42C was set to 45 degrees, and the maximum distance between thefacing sipe wall surfaces of the sipe chamfered portion 42 of the bentportion 46 was set to 5.5 mm.

In Example 1 without the bent portion 46, the tread pattern illustratedin FIG. 2 was set as a basic pattern. The distal end of the first sipe30 had a shape similar to the closed end of the first sipe 31 (see FIG.3B). In Examples 2 to 6, the tread pattern illustrated in FIG. 2 was setas a basic pattern.

Both in Conventional Example and Examples, the edge portions of thecenter main groove 12 were provided with groove chamfered portions andhad a zigzag shape. A “chamfered depth” in Tables 1 and 2 indicates aratio of the depth of the sipe chamfered portion 42 (a length from thetread surface to the deepest position of the sipe chamfered portion 42)with respect to the sipe depth of the first sipes 30, 31 (a total depthof the sipe main body portion 40 and the sipe chamfered portion 42).

The groove width and the groove depth of the center main grooves 11, 12were set to 9.3 mm and 8.3 mm, respectively, the groove width and thegroove depth of the shoulder main grooves 13, 14 were set to 11.3 mm,and the maximum groove width and the maximum groove depth of theshoulder lug grooves 35, 36 were set to 5.5 mm and 5.2 mm, respectively.

TABLE 1 Conventional Comparative Example Example Example 1 Example 2Example 3 Presence of lug grooves in regions of the Yes No No No Nointermediate continuous land portions 22, 23 Presence of the first sipes30, 31 No Yes Yes Yes Yes Presence of the sipe chamfered portion 42 NoNo Yes Yes Yes Presence of the bent portion 46 No No No Yes Yes Depth ofthe sipe chamfered portion 42 — — 0.4 0.4 0.2 Inclination angle of thefirst sipes 30, 31 with — 50 degrees 50 degrees 50 degrees 50 degreesrespect to the shoulder main grooves 13, 14 Steering stabilityperformance on dry road surface 100 105 105 105 110 Steering stabilityperformance on wet road surfaces 100 100 105 108 102 Pattern noise 100105 105 105 107

TABLE 2 Example 4 Example 5 Example 6 Presence of lug grooves in regionsof the No No No intermediate continuous land portions 22, 23 Presence ofthe first sipes 30, 31 Yes Yes Yes Presence of the sipe chamferedportion 42 Yes Yes Yes Presence of the bent portion 46 Yes Yes Yes Depthof the sipe chamfered portion 42 0.6 0.4 0.4 Inclination angle of thefirst sipes 30, 31 with 50 degrees 25 degrees 75 degrees respect to theshoulder main grooves 13, 14 Steering stability performance on dry roadsurface 102 102 102 Steering stability performance on wet road surfaces110 105 105 Pattern noise 102 105 105

As compared to Conventional Example, it can be seen that, in all ofExamples 1 to 6, steering stability performance on dry road surfaces andwet road surfaces was improved and pattern noise was reduced.

From comparison between Comparative Example and Example 1, it can beseen that steering stability performance on wet road surfaces wasimproved by providing the sipe chamfered portion 42 to the first sipe30.

From comparison between Example 1 and Example 2, it can be seen thatsteering stability performance on wet road surfaces was improved byproviding the bent portion 46 to the first sipe 30.

From Examples 2 to 4, it can be seen that steering stability performanceon dry road surfaces and wet road surfaces was improved by setting thedepth of the sipe chamfered portion 42 to a depth from 0.2 to 0.6 timeslarger than the total depth of the sipe main body portion 40 and thesipe chamfered portion 42 of each of the first sipes 30, 31.

From Examples 2, 5, and 6, it can be seen that steering stabilityperformance on dry road surfaces and wet road surfaces was improved andpattern noise was reduced in a case where the inclination angle of thefirst sipes 30, 31 with respect to the shoulder main grooves 13, 14 fellin a range from 25 degrees to 75 degrees.

This clearly demonstrates the effect of the pneumatic tire T accordingto the present embodiment.

While the pneumatic tire according to the embodiments of the presenttechnology is described above in detail, the present technology is notlimited to the above embodiments and may be improved or modified invarious ways within a range without departing from the essence of thepresent technology as a matter of course.

1. A pneumatic tire, comprising: a tread portion extending in a tirecircumferential direction, having an annular shape, and having a treadpattern, wherein the tread pattern comprising: two inner main groovesbeing positioned on both sides in a tire lateral direction with respectto a tire equator line of the pneumatic tire and being formed in anentire circumference in the tire circumferential direction; two outermain grooves being provided and sandwiching the two inner main grooveson an inner side in the tire lateral direction; an inner continuous landportion being sandwiched between the two inner main grooves and beingcontinuously formed in the entire circumference in the tirecircumferential direction; two intermediate continuous land portionsbeing sandwiched between one of the two inner main grooves and one ofthe two outer main grooves and between the other one of the two innermain grooves and the other one of the two outer main grooves,respectively, the two intermediate continuous land portions beingcontinuously formed in the entire circumference in the tirecircumferential direction, the two intermediate continuous land portionsbeing outward in the tire lateral direction of the inner continuous landportion; and first sipes being provided in regions of the twointermediate continuous land portions and extending inward in the tirelateral direction from the two outer main grooves, regions of the innercontinuous land portion and the two intermediate continuous landportions being not provided with lug grooves extending from the twoinner main grooves or the two outer main grooves, edges on both sides ofone of the two inner main grooves each comprising a groove chamferedportion having a chamfered width changing in the tire circumferentialdirection and forming a zigzag shape as seen from a tread surface of thetread portion, and the first sipes each including: a sipe main bodyportion having a constant distance between sipe wall surfaces on a sipebottom side in a depth direction of the first sipes; and a sipechamfered portion inclined so that the sipe wall surfaces are open tothe tread surface on a side of the tread surface of the first sipes, thesipe chamfered portion including, along an extending direction of thefirst sipe, a symmetric shape portion where two facing sipe wallsurfaces of the sipe chamfered portion are arranged being symmetric withrespect to a sipe center line of the first sipe, and an asymmetric shapeportion where the two facing sipe wall surfaces are arranged beingasymmetric with respect to the sipe center line, and in the asymmetricshape portion, one of the two facing sipe wall surfaces having a gradualinclined surface that inclines with respect to the tread surfacegradually compared to an other of the two facing sipe wall surfaces. 2.The pneumatic tire according to claim 1, wherein a sipe wall surfacebeing one of the two facing sipe wall surfaces comprises a firstchamfered surface and a second chamfered surface at different positionsin a sipe depth direction, an inclination angle of each of the firstchamfered surface and the second chamfered surface with respect to thedepth direction of the first sipes being different each other, and thesipe chamfered portion forms a bent shape of the bent portion.
 3. Thepneumatic tire according to claim 2, wherein the inclination angle ofthe first chamfered surface is identical to that of a counter chamferedsurface opposing the first chamfered surface.
 4. The pneumatic tireaccording to claim 2, wherein the inclination angle of the secondchamfered surface is larger than the inclination angle of the firstchamfered surface.
 5. The pneumatic tire according to claim 4, whereinthe second chamfered surface is positioned on the side of the treadsurface with respect to the first chamfered surface.
 6. The pneumatictire according to claim 2, wherein a chamfered width of the two facingchamfered surfaces is reduced as approaching to a closed end of the sipemain body portion.
 7. The pneumatic tire according to claim 1, whereinthe first sipes are provided to be inclined in the tire lateraldirection from the two outer main grooves to the inner continuous landportion and to be closed in the regions of the two intermediatecontinuous land portions, as seen from the tread surface, a surfacecontour shape of each of first sipes a of the first sipes, which extendsfrom an outer main groove A being one of the two outer main grooves,comprises: an extending portion extending constantly in an extensiondirection or with smooth change from the outer main groove A; and a bentportion provided on a side of a closed end portion of each of the firstsipes a, the bent portion bending each of the first sipes a from theextending portion and extending to a direction opposite a direction towhich the extending portion extends in the tire circumferentialdirection, in the bent portion, the sipe main body portion extends fromthe extending portion constantly in the extension direction or withsmooth change without being bent and is closed, and the sipe chamferedportion forms a bent shape of the bent portion, and narrow grooves eachbeing prevented from communicating with the bent portion are formedintermittently in the tire circumferential direction in a region of anintermediate continuous land portion α of the two intermediatecontinuous land portions in which the first sipes a are provided, and anextension direction of the narrow grooves is parallel with an extensiondirection of an edge of the surface contour shape on a side of the twoinner main grooves.
 8. The pneumatic tire according to claim 1, whereinthe first sipes are provided to be inclined in the tire lateraldirection from the two outer main grooves to the inner continuous landportion and to be closed in the regions of the two intermediatecontinuous land portions, as seen from the tread surface, a surfacecontour shape of each of first sipes a of the first sipes, which extendsfrom an outer main groove A being one of the two outer main grooves,comprises: an extending portion extending constantly in an extensiondirection or with smooth change from the outer main groove A; and a bentportion provided on a side of a closed end portion of each of the firstsipes a, the bent portion bending each of the first sipes a from theextending portion and extending to a direction opposite a direction towhich the extending portion extends in the tire circumferentialdirection, in the bent portion, the sipe main body portion extends fromthe extending portion constantly in the extension direction or withsmooth change without being bent and is closed, and the sipe chamferedportion forms a bent shape of the bent portion, the pneumatic tire has amounting direction that is specified with respect to a vehicle, and theouter main groove A is instructed, +−by the mounting direction, to bepositioned on an outer vehicle side with respect to an outer main grooveB of the two outer main grooves, the outer main groove B being differentfrom the outer main groove A.
 9. The pneumatic tire according to claim1, wherein the first sipes are provided to be inclined in the tirelateral direction from the two outer main grooves to the innercontinuous land portion and to be closed in the regions of the twointermediate continuous land portions, as seen from the tread surface, asurface contour shape of each of first sipes a of the first sipes, whichextends from an outer main groove A being one of the two outer maingrooves, comprises: an extending portion extending constantly in anextension direction or with smooth change from the outer main groove A;and a bent portion provided on a side of a closed end portion of each ofthe first sipes a, the bent portion bending each of the first sipes afrom the extending portion and extending to a direction opposite adirection to which the extending portion extends in the tirecircumferential direction, in the bent portion, the sipe main bodyportion extends from the extending portion constantly in the extensiondirection or with smooth change without being bent and is closed, andthe sipe chamfered portion forms a bent shape of the bent portion,second sipes are provided in a region of an intermediate continuous landportion β of the two intermediate continuous land portions, which issandwiched between an outer main groove of the two outer main groovesdifferent from the outer main groove A and one of the two inner maingrooves, the second sipes extending from one of the two inner maingrooves and being closed without communicating with the outer maingroove, third sipes are provided in the region of the inner continuousland portion, the third sipes extending from an inner main groove of thetwo inner main grooves, which is in contact with the intermediatecontinuous land portion β, to the other inner main groove and beingclosed without communicating with the other inner main groove, andinclination directions of the second sipes and the third sipes withrespect to the tire lateral direction and positions thereof in the tirecircumference are set, and the second sipes are positioned on extensionlines of the third sipes.
 10. The pneumatic tire according to claim 8,wherein, second sipes are provided in a region of an intermediatecontinuous land portion β of the two intermediate continuous landportions, which is sandwiched between an outer main groove of the twoouter main grooves different from the outer main groove A and one of thetwo inner main grooves, the second sipes extending from one of the twoinner main grooves and being closed without communicating with the outermain groove, second sipes are provided in a region of an intermediatecontinuous land portion β of the two intermediate continuous landportions, which is sandwiched between the outer main groove differentfrom the outer main groove A and one of the two inner main grooves, thesecond sipes extending from one of the two inner main grooves and beingclosed without communicating with the outer main groove, as seen fromthe tread surface, first sipes b of the first sipes, which are providedin a region of the intermediate continuous land portion β, and thesecond sipes are inclined to different directions in the tirecircumferential direction as extending inward in the tire lateraldirection.
 11. The pneumatic tire according to claim 1, wherein, as seenfrom the tread surface, the first sipes provided in the regions of thetwo intermediate continuous land portions are inclined to differentsides in the tire circumferential direction as extending inward in thetire lateral direction.
 12. The pneumatic tire according to claim 1,wherein an outer land portion is provided on an outer side of the outermain groove B of the two outer main grooves in the tire lateraldirection, a circumferential auxiliary groove and outer lug grooves areprovided in a region of the outer land portion, the circumferentialauxiliary groove formed in the entire circumference in the tirecircumferential direction, the outer lug grooves extending in the tirelateral direction from the outer side in the tire lateral direction andbeing closed without communicating with the outer main groove B, and theouter lug grooves intersect the circumferential auxiliary groove. 13.The pneumatic tire according to claim 1, wherein the first sipes areprovided to be inclined in the tire lateral direction from the two outermain grooves to the inner continuous land portion and to be closed inthe regions of the two intermediate continuous land portions, as seenfrom the tread surface, a surface contour shape of each of first sipes aof the first sipes, which extends from an outer main groove A being oneof the two outer main grooves, comprises: an extending portion extendingconstantly in an extension direction or with smooth change from theouter main groove A; and a bent portion provided on a side of a closedend portion of each of the first sipes a, the bent portion bending eachof the first sipes a from the extending portion and extending to adirection opposite a direction to which the extending portion extends inthe tire circumferential direction, in the bent portion, the sipe mainbody portion extends from the extending portion constantly in theextension direction or with smooth change without being bent and isclosed, and the sipe chamfered portion forms a bent shape of the bentportion, and the asymmetric shape portion being positioned in the bentportion.
 14. A pneumatic tire, comprising: a tread portion extending ina tire circumferential direction, having an annular shape, and having atread pattern, wherein the tread pattern comprising: two inner maingrooves being positioned on both sides in a tire lateral direction withrespect to a tire equator line of the pneumatic tire and being formed inan entire circumference in the tire circumferential direction; two outermain grooves being provided and sandwiching the two inner main grooveson an inner side in the tire lateral direction; an inner continuous landportion being sandwiched between the two inner main grooves and beingcontinuously formed in the entire circumference in the tirecircumferential direction; two intermediate continuous land portionsbeing sandwiched between one of the two inner main grooves and one ofthe two outer main grooves and between the other one of the two innermain grooves and the other one of the two outer main grooves,respectively, the two intermediate continuous land portions beingcontinuously formed in the entire circumference in the tirecircumferential direction, the two intermediate continuous land portionsbeing outward in the tire lateral direction of the inner continuous landportion; and first sipes being provided in regions of the twointermediate continuous land portions and extending inward in the tirelateral direction from the two outer main grooves, regions of the innercontinuous land portion and the two intermediate continuous landportions being not provided with lug grooves extending from the twoinner main grooves or the two outer main grooves, edges on both sides ofone of the two inner main grooves each comprising a groove chamferedportion having a chamfered width changing in the tire circumferentialdirection and forming a zigzag shape as seen from a tread surface of thetread portion, and the first sipes each including: a sipe main bodyportion having a constant distance between sipe wall surfaces on a sipebottom side in a depth direction of the first sipes; and a sipechamfered portion inclined so that the sipe wall surfaces are open tothe tread surface on a side of the tread surface of the first sipes, asipe wall surface being one of two facing sipe wall surfaces comprises afirst chamfered surface and a second chamfered surface at differentpositions in a sipe depth direction, an inclination angle of each of thefirst chamfered surface and the second chamfered surface with respect tothe depth direction of the first sipes being different each other, thesipe chamfered portion forms a bent shape of the bent portion, and theinclination angle of the second chamfered surface is larger than theinclination angle of the first chamfered surface.